Incorporation of residual lime can ameliorate subsoil acidity promptly and improve crop performance on sandy soils of the semi-arid regions of Western Australia

Abstract

Background and Aims Repeated surface application of lime to acidic soil improves farm productivity but cannot manage subsoil acidity promptly. Lime accumulation in topsoil prompted this study to evaluate the role of strategic tillage as a method to swiftly improve subsoil acidity, crop root growth, and yield without additional lime. Methods We measured residual lime (carbonate concentration), pH and exchangeable aluminium concentration (EAC) in 2-cm layers in the top 10 cm of soils from three long-term lime experiments at Wongan Hills (WH), Northam (NO) and Merredin (ME). We then incorporated topsoil from 0–4 cm (containing the highest amount of residual lime) at eight incorporation rates with the most acidic subsoil from 20–30 cm depth of the same profile and incubated for six weeks before re-measuring pH and EAC and growing wheat and barley to assess the impact on root growth. In addition, we conducted a field experiment at WH by rotary hoeing both limed and untreated control plots to 25 cm depth in 2018 and grew wheat, canola and barley in 2018, 2019 and 2020, respectively, to measure the impact on soil parameters and crop performance. Results A significant amount of residual lime was concentrated in the top 4 cm of soil at all three sites. We measured a total of 1.7, 1.8 and 1.3 t/ha of residual lime in the topsoil (0–10 cm) for the limed plots at WH, NO and ME, respectively. The incorporation of 5%, 10% and 25% topsoil containing residual lime from NO, WH and ME, respectively, with the acidic subsoil was enough to increase soil pH to the target level and to decrease soil EAC significantly and hence improved wheat and barley root length by up to 2 and 13-fold. In the field experiment at WH, the incorporation of residual lime significantly increased subsoil pH by up to 0.7 units, decreased EAC and improved canola yield and water use efficiency. Conclusion We concluded that with a good surface liming history, the incorporation of topsoil containing sufficient residual lime with the acidic subsoil may offer a quick amelioration of subsoil acidity without further lime application.